In 3GPP (3rd Generation Partnership Project), LTE (Long Term Evolution, or Evaluated UTRA and UTRAN) is under investigation as a next-generation radio communication standard (Non-Patent Document 1 illustrated below, for example).
In LTE, OFDM (Orthogonal Frequency Division Multiplexing) is utilized for a downlink from a base station to a terminal, and SC-FDMA (Single-Carrier Frequency Division Multiple Access) is utilized for an uplink from the terminal to the base station.
The OFDM is a transmission method in which a frequency band is divided into a plurality of sub-carriers and data are transmitted while carried directly on each sub-carrier. On the other hand, the SC-FDMA is a transmission method in which data transformed by DFT (Discrete Fourier Transform) is carried on the sub-carrier and is transmitted. FIG. 18 and FIG. 19 illustrate configuration examples of signal processing circuits employed in SC-FDMA and OFDM, respectively. Referring to FIG. 18, a DFT (Discrete Fourier Transform) unit 101 is included in front of a sub-carrier mapping unit, and DFT-processed signal is input successively into the sub-carrier mapping unit 102, an IDFT (Inverse Discrete Fourier Transform) unit 103, and a CP (Cyclic Prefix) insertion unit 104. Referring to FIG. 19, transmission data is input into a sub-carrier mapping unit 111 and then input successively into an IDFT unit 112 and a CP insertion unit 113.
On the other hand, the base station or the terminal uses an amplifier to transmit data. The amplifier has a problem that linearity cannot be maintained and the data are distorted, when an input power is large. When the data are distorted, out-of-band emission power increases. An upper limit value of the out-of-band emission power (hereinafter, “ACLR”) is determined by an ACLR (Adjacent Carrier Leakage Ratio) standard, and when the data distortion is large, the ACLR can no longer be satisfied.
In consideration of the ACLR, the SC-FDMA is a favorable method due to its low PAPR (Peak to Average Power Ratio), and therefore SC-FDMA is applied to the uplink from the terminal in LTE.    Non-Patent Document 1: 3GPP TS 36. 211V8. 0. 0 (2007-09)    Non-Patent Document 2: Hikmet Sari, Geroges Karam and Isabell Jeanclaude, “Transmission Techniques for Digital Terrestrial TV Broadcasting”, IEEE Communication Magazine, pp. 100-109, February 1995